1. Field of the Invention
The present invention relates to insufflation devices and, in particular, to a medical insufflation device having an automatic control device with feedback sensors for regulating and controlling the flow of gas into an inflatable body cavity.
2. Description of the Prior Art
Typically, prior to hysteroscopy, an insufflation device is employed to expand the cavum uteri with a gas through a probe or an endoscope channel. As the cavum uteri opens, a desired intrauterine pressure is established. Under normal anatomical circumstances, the insufflation pressure should preferably lie between approximately 0.5.times.10.sup.4 and 1.0.times.10.sup.4 Pa, and the gas flow (or mass flow) should preferably be between about 30 to 40 ml/min. Of course, a given maximum intra-uterine gas pressure should not be exceeded for medical reasons.
During a simulated operation, and prior to an actual examination, an operator checks or obtains permissible maximum values such, for example, as a maximum intra-uterine pressure value for the patient. It has been found that the maximum permissible insufflation pressure is in the range of approximately 1.99.times.10.sup.4 to 2.66.times.10.sup.4 Pa and the maximum gas flow should not exceed about 100 ml/min or, preferably, about 70 ml/min.
When a hysteroscope is moved back and forth during an examination, the intra-uterine pressure may change. However, after a short time a steady state or equilibrium pressure is re-established by the insufflation device. Naturally, the more the pressure in the body cavity rises, the smaller the quantity of gas flowing into the cavum uteri. When the pressure between the insufflation device and the cavum uteri reaches equilibrium, the flow of gas stops. With tubes closed, the intra-uterine pressure will rise to a pre-established level while the gas flow falls to zero.
In a normal operation (i.e. without automatic operation), and after the initial check for permissible maximum values, the operator manually monitors the maintenance of the maximum pressure and flow values, and constantly checking the displays of an insufflation device. When a hysteroscope is moved back and forth during examination, the insufflation pressure in the cavum uteri may change due to gas leakage through the scope itself, and/or through any other passages associated with the uterus being operated on. In response, the operator is required to make appropriate adjustments to the valves of the insufflation device so as to compensate for such pressure drops.
In order to relieve the operator (such, for example, as the examining physician) from having to perform these distracting mechanical tasks including instrument readings and the like, it is desirable that these tasks be performed automatically. In particular, it is desirable to have an insufflation device which automatically monitors and maintains intra-uterine pressure and gas flow at predetermined maximum values by automatically performing appropriate valve adjustments during examination.
German publication DE-C-39 22 746 discloses an insufflation device which comprises a gas suction circuit having an automatic shut-off. Tile suction circuit includes a pump whose suction side is connected to a flow output meter and a pressure transducer, and whose pressure side is connected to an endoscope. Measurement data from the pressure transducer and flow output meter are communicated to an electronic evaluation system for processing so that if any disturbance is detected in the suction circuit, the pump is automatically shut off. The device of the German publication, however, does not automatically monitor and maintain reduced pressure in an inflatable body cavity during insufflation.